Phenology, behavior and infestation levels of the invasive small cypress bark beetle, Phloeosinus aubei, on some cultivars of Thuja and Juniper spp., in Hungary.
The invasive small cypress bark beetle, Phloeosinus aubei (Coleoptera, Curculionidae, Scolytinae) has two flights in Central-Europe, however, it was unclear, whether this corresponds to two reproductive periods, when nuptial chambers are formed and galleries initiated. The aim of this study was to clarify the life-cycle of P. aubei in Hungary, representing populations in the range of invasion, and to compare preferences towards some popular cultivars of Thuja and Juniper ornamental trees. In order to reveal which is the pioneering gender, and to confirm females' preferences between healthy and broken trunks behavioral tests were conducted. Results showed that adults prepare hibernation tunnels from August until October. Sex ratio of overwintering adults was nearly equal. The significantly highest number of hibernation tunnels was found on Thuja plicata Atrovirens (mean±S.E.: 6.0±0.7/tree), followed by T. occidentalis Smaragd (2.2±0.8), Juniperus chinensis Spartan (1.6±0.6), and J. scopulorum Blue Arrow (0.2±0.2). Nuptial chambers were made from April until June, by singly females, never by males. Females chose broken, drying trunks over healthy ones. Adults of the next generation emerged from the galleries from August until October. By October adults emerged from 94% of the galleries, and larvae were found only in 6% of the galleries. These results showed that the autumn flight of P. aubei is linked to making hibernation tunnels, while the spring flight to producing nuptial chambers. The latter corresponds to a single reproductive period per year. Control measures against adults should be timed to these two specific periods of the season.